The Volcano Adventure Guide: Excellent information and background for anyone wishing to visit active volcanoes safely and enjoyably. The book presents guidelines to visiting 42 different volcanoes around the world.

Krakatau, a small island group in the Sunda Strait between the islands of Sumatra and Java is one of the world's most famous volcanoes. It is a mostly submerged caldera with 3 outer islands belonging to the rim and a new cone, Anak Krakatau, that has been forming a new island since 1927 and remains highly active.
Krakatau exploded spectacularly in a devastating Plinian eruption 1883 that killed more than 30,000 people (mostly by the huge tsunamis triggered by the eruption). The eruption was one of the first global news events after telegraph lines had connected the different continents.

Krakatau, a small island group in the Sunda Strait between the islands of Sumatra and Java is one of the world's most famous volcanoes. It is a mostly submerged caldera with 3 outer islands belonging to the rim and a new cone, Anak Krakatau, that has been forming a new island since 1927 and remains highly active.
Krakatau exploded spectacularly in a devastating Plinian eruption 1883 that killed more than 30,000 people (mostly by the huge tsunamis triggered by the eruption). The eruption was one of the first global news events after telegraph lines had connected the different continents.

Satellite image showing what appears to be a major collapse- via Twitter/Maarten Van Daele.

News continues to develop in the aftermath of the tragic disaster.

Videos (https://www.youtube.com/watch?v=EQmeJdIBTsQ https://twitter.com/hudasafiro/status/1076805858518982657) have surfaced that seem to show that at least part of the cone of Anak Krakatau has collapsed.

A violent Surtseyan eruption can be seen, which could certainly be powerful enough to generate the ash plume to 55,000ft that continues to emanate from the volcano according to the Darwin VAAC.

There is still a lack of clarity surrounding the situation, however the fact that a high ash plume has been observed for many hours suggests the eruption could reach VEI 4, with a possibility that it already has.

A major explosive eruption might have occurred at the volcano earlier this morning. VAAC Darwin spotted a large cloud, possibly an ash plume from the eruption reaching approx. 55,000 ft (15 km) altitude and drifting S and SW. ...
[details]

Satellite image showing what appears to be a major collapse- via Twitter/Maarten Van Daele.

News continues to develop in the aftermath of the tragic disaster.

Videos (https://www.youtube.com/watch?v=EQmeJdIBTsQ https://twitter.com/hudasafiro/status/1076805858518982657) have surfaced that seem to show that at least part of the cone of Anak Krakatau has collapsed.

A violent Surtseyan eruption can be seen, which could certainly be powerful enough to generate the ash plume to 55,000ft that continues to emanate from the volcano according to the Darwin VAAC.

There is still a lack of clarity surrounding the situation, however the fact that a high ash plume has been observed for many hours suggests the eruption could reach VEI 4, with a possibility that it already has.

A major explosive eruption might have occurred at the volcano earlier this morning. VAAC Darwin spotted a large cloud, possibly an ash plume from the eruption reaching approx. 55,000 ft (15 km) altitude and drifting S and SW. ...
[details]